This invention relates to an electric fuse capable of meeting the requirements of the Underwriter's RK1 classification.
Another object of this invention is to provide an electric fuse that lends itself to semi-automatic, or fully automatic, production.
Another object of this invention is to provide a fuse whose low current interruption is effected by a contact in form of a spring-biased plunger the degree of heat absorbing capacity of which controls the time-lag of the fuse.
Such a plunger has the advantage of providing a long contact travel which can be further extended by allowing the plunger to travel into the terminal cap having the rejection feature referred-to above.
Such a plunger has further the advantage that its mass, and hence the time-lag of the fuse, can readily be increased, if necessary.
Another object of the invention is to provide a fuse having a heating element of the required resistivity and not being subject to the limitations of a coil heater of wire. Conventional coil heaters become very critical at higher current ratings owing to the lower resistance needed under such conditions. To be more specific, coil heaters for high-current ratings become very critical because the wire coils are short and the diameter of the wire is large. Strip heaters are not subject to this drawback. The resistance material of which they are made is more manageable in comparison to coil heaters and allows for larger working dimensions and tolerances.
Other objects and advantages of the invention will become more apparent as this specification proceeds.